Table 5

Statistics of Background at Minimum

Tube Sigma/N N Ci Inferred Primary
Events/14 sec2		 Rate due to
CR		 Pe/event
Y		 Photocathode
Area
A1 B1 A B I=(Sigma/NCi)-2 [NavgxCi] [Y=NavgCi/I] (cm+2)
U1 .26 .19 18.4 20.2 1 19 19 1 3.2
U2 .383 .26 14.6 14.6 1 10 15 13 3.2
U3 ---3 --- 9.6 10.4 1 (4)4 10 1(2)3 0.7
V15 (0.14) (4700) 0.52 (14)6 (2450) (150-200)5 1.8
V2 .20 .16 2163 2295 0.68 14 1500 107 1.8
V3 .031 .034 3024 2982 0.20 37 600 16.2 5

1.
Data "A" represents 40 points (14 sec integration each) for standard minutes 91-100 of standard orbit 47. Data were recorded during satellite orbit number 4306. Data "B" represents the same interval and time as data "A", except that it refers to standard minutes 41-50.

2.
The standard deviation calculated,

Sigma = [Sumi=1,K(Ni-Navg)2] / K,

is essentially Sigma = SigmaCR, since the fluctuations due to other components (phosphorescence) will be ħSqrt(N), or 40-65 on V1 and V2, compared to the observed fluctuations of 400-600 cts/14 sec. Then Sigma/NCR = Sigma/NCi = Sqrt(IY)/IY, where I is the inferred number of primary events/14 sec and Y is the yield in photoelectrons/event. Ci is a correction factor defined in the text.

3.
Due to scaling of 23 and 25 on U2 and U3 respectivily, the statistics cannot be derived directly at such low values of N. We assume these tubes are similar to U1 except for area, the area of U3, in agreement with the statistics seen at particle maximum where the scaling is not so important in statistical analyses.

4.
I(U3) is defined as I(U1) x Area(U3)/Area(U1).

5.
V1 was not on at this interval. The value Y(V1) is based on a recent test during which data was stored every 1/8 sec instead of every 14 sec. Since the primary flux is 1-2/sec, the yield of each event can be seen separately. The test was done at a maximum background region, near orbit 12000. The other entries for V1 are inferred from I and Ci. A yield of 130 pe/event would be more consistent with the values of Ci and Nmin given in table 4.

6.
Assumed equal to I(V2).
Return to main paper.